This invention relates generally to record and playback systems used with discs, drums, or similar rotating surfaces, and particularly to systems equipped to locate an addressed track on the surface by moving a transducer means in a direction perpendicular to the tracks.
Prior art information storage systems utilize magnetic and optical recording tracks on tape, disc, and drum surfaces. The packing density, which is inversely proportional to the track spacing, has been significantly increased in optical systems utilizing the laser as the optical transducer. Nevertheless, the known systems do not provide for noncontinuous recording when the track spacing is very close because of the difficulty involved in precisely relocating the transducer after it has been moved with respect to the recording surface. Several problems relating to noncontinuous recording systems have heretofore remained without satisfactory solutions. One such problem is the mechanical positioning of the medium after removal and remounting for recording subsequent tracks. Another problem is caused by the eccentricity errors of the surface resulting from distortion and deformation of the surface structure by thermal effects, inter alia. The eccentricity alters the track position profiles of previously recorded tracks and cause track spacing deviations that may exceed the system track spacing. As a result, a new track might overlay a previously recorded track and the information recorded thereon would be lost. The present invention provides means for solving these problems.
According to the present invention, an optical record and playback apparatus is provided with an optical transducer that is controlled to record tracks that have a contour conforming to the contour of a reference track or of any recorded track. Compensation for eccentricity errors is thus provided allowing for recording tracks on a partly recorded surface with spacing between the tracks that is less than the eccentricity errors.